The present invention relates to a wheel assembly state informing system and a wheel assembly state informing method for acquiring pieces of wheel assembly information on wheel assemblies of any one of various kinds of vehicles such as a vehicle having at least four or more wheels or a two-wheel vehicle and informing states of the respective wheel assemblies based on those pieces of information. Those vehicles include passenger vehicles, buses, and trucks. The pieces of wheel assembly information include, for example, pieces of information on tires as components of the wheel assemblies, such as internal pressure data and temperature data on the tires.
Nowadays it has been proposed to fit a tire internal pressure warning system to each of various kinds of vehicles such as passenger vehicles, buses, trucks, and even motorbikes, which have wheel assemblies that are constructed by mounting tires on rims respectively. The tire internal pressure warning system constantly monitors an internal pressure of a tire and informs an abnormality in the internal pressure of the tire when necessary.
A conventionally proposed tire internal pressure warning system is installed in a vehicle equipped with a plurality of wheel assemblies. For example, pressure sensors and transmitters are provided respectively in tire hollow regions of the plurality of wheel assemblies. The tire hollow regions are surrounded by inner peripheral faces of tires and bottom faces of rim bottoms respectively and filled with air. The pressure sensors mounted to the wheel assemblies respectively measure internal pressures of the tire hollow regions. Internal pressure data on the respective tire hollow regions are transmitted by wireless transmission from the transmitters mounted to the respective wheel assemblies, respectively.
On the other hand, a receiver and an indicator are provided on a vehicle body side. The receiver receives internal pressure data that are transmitted by wireless transmission from the transmitters respectively. Based on the respective internal pressure data received, the receiver monitors whether or not states of the tires of which the internal pressure data have been obtained are abnormal respectively. The states of the tires refer to internal pressure levels of the tire hollow regions. The indicator is provided to inform an operator of the vehicle of the states of the respective tires. When the receiver determines that the state of a specific one of the plurality of tires of the vehicle is abnormal, the indicator informs the operator of the vehicle that the state of the specific one of the tires (the internal pressure level of the tire) is abnormal.
It is important in this tire internal pressure warning system that the operator of the vehicle surely grasps which one of the plurality of the tires outfitted to the vehicle is in an abnormal state. If the operator of the vehicle can surely grasp which one of the tires is in an abnormal state, an advantage is obtained especially in the case where an abnormality occurs in the tire. For example, the operator of the vehicle can swiftly specify the tire in which the abnormality has occurred, and can quickly perform operations of supplying a supplementary air pressure, replacing the tire, and the like.
In general, a plurality of tires mounted to a vehicle do not have characteristic appearances that are different among the tires and make the tires mutually distinguishable in external appearance. Therefore, the operator of the vehicle used to identify the plurality of tires respectively according to mounting positions of the tires (e.g., a front-right wheel, a front-left wheel, a rear-right wheel, a rear-left wheel, etc.). Thus, with the conventional tire internal pressure warning system, the operator of the vehicle used to grasp states of the individual tires by causing the indicator to indicate the mounting positions of the tires and the states of the respective tires in an associative manner.
One such tire internal pressure warning system (first tire internal pressure warning system) has been proposed which utilizes a correlation between transmitters mounted to respective tires and pieces of information on mounting positions of the respective tires. In the first tire internal pressure warning system thus configured, the correlation between the transmitters provided in the respective tires and the pieces of information on the mounting positions of the respective tires (first correlation) is prestored in a receiver. The receiver receives internal pressure data on the respective tires which have been transmitted from the transmitters mounted to the respective tires. Using the first correlation, the receiver determines the mounting positions of the respective tires corresponding to the respective internal pressure data received. The first tire internal pressure warning system as described above is disclosed in, for example, JP 8-505939 A.
Another tire internal pressure warning system (second tire internal pressure warning system) has also been proposed which uses a correlation between pieces of information on positions of a plurality of tire houses of a vehicle body and pieces of information on positions of antennas provided to the tire houses respectively. In this second tire internal pressure warning system, a correlation between pieces of information on mounting positions of the antennas and pieces of information on mounting positions of the tire houses (second correlation) is prestored in a receiver. The respective antennas receive respective internal pressure data that have been transmitted from transmitters mounted to the tires outfitted to the vehicle. That is, the respective antennas receive internal pressure data on the tires, which are transmitted from the transmitters mounted to the tires outfitted to the vehicle. The receiver receives the internal pressure data received by the respective antennas respectively, and specifies the internal pressure data transmitted from the transmitter closest to the tire house provided with each of the antennas for each antenna. Using the aforementioned second correlation, the receiver determines positions of the tire houses corresponding to the respective internal pressure data received by the respective antennas. The second tire internal pressure warning system as described above is disclosed in, for example, JP 10-104103 A.
In the aforementioned first warning system, the transmitters mounted to the plurality of tires respectively hold specific pieces of identification information (ID's) respectively. The respective transmitters then transmit the specific pieces of identification information (ID's) as well as the internal pressure data to the receiver. The correlation between the respective pieces of identification information on the respective transmitters and the mounting positions of the respective tires provided with the respective transmitters is prestored in a memory of the receiver. Based on this stored correlation, the receiver determines the mounting positions of the tires corresponding to the received internal pressure data respectively. The indicator then associates the acquired internal pressure data with the mounting positions of the corresponding tires and indicates them. By visually checking the indicated data, the operator of the vehicle can respectively specify the tires from which the indicated pieces of wheel assembly information (internal pressure data) are acquired respectively, according to the mounting positions of the tires.
In the second warning system, the tire houses of the vehicle body are provided with antennas respectively. The pieces of information on the mounting positions of the respective antennas (e.g., the front-right tire house, the front-left tire house, the rear-right tire house, the rear-left tire house, etc.) are prestored in a memory of the receiver connected to the respective antennas. The receiver receives internal pressure data received by the respective antennas, and specifies the internal pressure data transmitted from the transmitters closest to the tire houses provided with the respective antennas (i.e., the transmitters mounted to the tires closest to the respective antennas) for each antenna. More specifically, the receiver extracts internal pressure data with a maximum signal power from a plurality of internal pressure data received by one of the antennas. The receiver then specifies the extracted internal pressure data as the internal pressure data transmitted from the transmitter closest to the tire house provided with the one of the antennas. Then, using the aforementioned second correlation, the receiver respectively determines the positions of the tire houses corresponding to the internal pressure data received by the receiver. In the second warning system, the mounting positions of the tires corresponding to the internal pressure data received by the receiver are specified respectively from the positions of the tire houses mounted with the antennas. The indicator then associates the acquired internal pressure data with the mounting positions of the corresponding tires respectively, and indicates them. By visually checking the indicated data, the operator of the vehicle can respectively specify the tires from which the indicated pieces of wheel assembly information (internal pressure data) are acquired, according to the positions of the tire houses.
In the vehicle, however, a so-called rotation of the wheel assemblies including the tires, that is, a permutation of the mounting positions of the wheel assemblies in the vehicle is carried out. This rotation of the wheel assemblies is carried out every time the vehicle covers a certain running distance or if need arises, so as to prevent life of the tires from being reduced due to the occurrence of partial abrasion of tire tread portions. The transmitters are fixed to the hollow regions of the tires. Therefore, even when the rotation of the wheel assemblies is carried out, the transmitters remain fixed to the wheel assemblies whose mounting positions are changed. In other words, the wheel assemblies whose mounting positions are changed are set at different mounting positions while the transmitters remain fixed. Therefore, the correlation between the pieces of identification information on the transmitters and the mounting positions of the wheel assemblies changes every time the rotation is carried out.
In the case where such a rotation of the wheel assemblies is carried out, the first correlation stored in advance becomes different from an actual correlation after the rotation of the wheel assemblies in the first tire internal pressure warning system. This causes a problem in that after the rotation of the wheel assemblies, the tires corresponding to the internal pressure data received by the receiver (the tires of which the internal pressure data are received) cannot be accurately specified. In order to accurately determine the tires corresponding to the respective internal pressure data received by the receiver after the rotation of the wheel assemblies as well, an associating operation for the correlation needs to be performed again every time a rotation of the wheel assemblies is carried out. This associating operation is troublesome and may lead to erroneous storage of a correlation.
In the second warning system, the tires corresponding to the internal pressure data received by the receiver are determined respectively according to the positions of the antennas that have received the internal pressure data (the positions of the tire houses mounted with the antennas that have received the internal pressure data). Therefore, in a vehicle such as a truck in which a plurality of tires are installed adjacently in a single tire house, the internal pressure data received by the receiver cannot be specified.
To configure the second warning system described above, it is necessary to install the plurality of antennas in the vicinity of each of the tire houses. Thus, very troublesome operations such as an operation of installing those antennas and an operation of wiring cables for connection are required. In particular, when a vehicle currently unmounted with a tire internal pressure warning system is newly mounted with the tire internal pressure warning system, there are problems in that troublesomeness and difficulty arise in a mounting operation and that an immeasurable cost and an enormous amount of time are required.